Contrary to what many people believe, there is not one psychotherapy that is more effective than others (Wampold et al.). The main factors helping in therapy is the therapeutic relationship, having structured goals to work towards, and a rationale that explains one's suffering.
Bruce Wampold is one of the most well-known researchers on studying the contributing factors on a good outcome in psychotherapy. Though a certain therapeutic approach can be more effective in certain specific conditions, the biggest factor influencing whether therapy works is whether you have a good therapeutic relationship (i.e. whether you get along, and feel heard). This seems logical, as it may be more easily to open up to a stranger about your problems if you feel welcome and heard.
Next to that, of course any treatment ought to establish some goals to work towards. However, these goals may change during therapy as a new situation may require some adaptation on what the desired outcome is supposed to be of the treatment. Generally any change of goals ought to be openly and clearly discussed, and adapted in one's treatment plan.
Finally, any effective therapy does not only create a healthy bond between client and therapist, and established structured goals, but also provides a clear rationale or explanation for why the problems/issues one is facing occur in the first place. We are often confused and demoralized when starting a treatment and good explanation of one's situation can help us understand the cause of our suffering and also a way to get better.
Check out the link for a good overview on Bruce Wampold's latest research ideas: http://societyforpsychotherapy.org/what-do-we-know-about-psychotherapy-and-what-is-there-left-to-debate/